On the other end of the spectrum is shot peening. Using larger media is an effective way to work the surface of metal. Some leaf springs are shot peened to reduce surface stress which reduces the formation of cracks and improves the life of the spring.

I use 60 grit Aluminum Oxide to sand blast memorial engravings in my park. There are all different blast materials with different abrasive qualities, similar to sand paper. Roughly 90psi-125psi is used. If the metal on the cabinets is thin I can see how it would deform them.

Also - the worst thing to sandblast, from a distortion perspective, is a big flat sheet of metal. You'd have been ok, I think, if you had them sandblast a curved front FJ40 fender or something that had some inherent strength from its shape.